unable to mail a member?

Hi,

As a member on this site for a couple of years, I've been able to mail other members without any problem but after trying to do so again today, I received this message even though I am not a new member: 'Your message hasn't been sent. In order to prevent issues, the private message system is not fully activated for new users. Have you presented yourself on the forum ? Please exchange a few messages with us on the forum, and we will fully activate the private message system. Thank you !'

Why?

Thanks!
celticnik